Delphi IDE uses InstallAware as installer in last few releases (2010, XE, XE2, XE3, XE4). Using the normal setup.exe installation will copy a few GB of files into c:\\progr
Partial answer here.
Is it advisable to delete those files manually after installation too?
Of course, official answer is NO. But you actually can delete these files at the cost of losing installer's "Repair" capability. (Repair is standard MSI feature, and InstallAway is merely yet another front-end for MSI). Also, it will render any manual restoration of particular file impossible, since files are stored in encrypted 7-zip archives on distribution medium (yet another unfriendly feature).
Unfortunately, I do not know any way to disable creation of such local copy of distribution medium.